The present invention relates to an image forming apparatus operable with a disposable supply being loaded in a body thereof.
It is a common practice with a copier, facsimile apparatus, printer or similar image forming apparatus to load various disposable supplies in a body of the apparatus. For example, an image forming apparatus of the type using a developing unit for developing an electrostatic latent image formed on a photoconductive element or similar image carrier by a developer is operable with a developer cartridge. The developer cartridge is loaded in the body of the apparatus for supplying a developer and is a typical disposable supply. Another typical supply is a silicone oil tank which may also be loaded in the apparatus. Such various supplies are individually replaced with new ones as needed. It has been customary to replace desired one of the supplies by opening a large front door which is mounted on the apparatus body. This is undesirable from the safety standpoint because when the front door is opened, various movable parts such as paper feed rollers and timing belts and various electrical parts such as motors and solenoids are uncovered.
An implementation heretofore proposed against the above hazard is an interlocking device which automatically interrupts the operation of the apparatus, i.e., mechanical motions and current supply when the front door is opened for the replacement of a supply. However, interrupting the operation of the apparatus every time a supply is replaced lowers the productivity (number of papers produced with images per unit time). Thus, prior art image forming apparatuses are incapable of continuing the image forming operation while insuring safety manipulations for the replacement of a supply, i.e., achieving satisfactory productivity. Further, since various knobs and other numerous parts such as for the removal of a jamming sheet are densely arranged inside of the front door, a person intending to replace a particular supply is often perplexed resulting in the operation efficiency being lowered.
In a prior art copier or similar image forming apparatus which develops an electrostatic latent image provided on an image carrier by using a developer in the form of powder, the operation is automatically stopped when the developer almost runs out or when a predetermined number of further copies are produced after such a near-end condition has been reached. When the developer is implemented by a two-component developer which is the mixture of toner and carrier, the copying operation is inhibited until the toner supplied to the apparatus or the toner cocnentration in the developer exceeds a predetermined amount. A drawback with this kind of control is that the downed condition of the copier continues until the supply of toner, preventing a person from producing urgent copies or forcing a person to give up copying when only a few more copies suffice. This limits the productivity of copies (number of copies per unit time).
This kind of developing unit may be operated with a developer cartridge which is an example of supplies as stated earlier. In the case that such a developing unit is so constructed as to allow a developer cartridge into and out of its body through an opening which is formed through a housing portion, there is a fear that the operator's hand is carelessly put into a cartridge inserting and removing path via the opening while the used cartridge is removed. Touching various movable members arranged around the path is very dangerous. It is therefore impossible to adopt a system which allows a developer cartridge to be replaced without interrupting the operation of the apparatus, unless such hazards are removed.
A developing unit of the type described includes an agitator or similar agitating member for preventing the developer stored in a developer supply chamber or in the apparatus body itself from blocking. When a developer cartridge is used with such a developing unit and loaded and unloaded through the opening which is formed through the housing portion of the apparatus body as previously stated, the agitating member which is rotating is hazardous for the operator who may inadvertently insert the hand into the cartridge inserting and removing path via the opening. Preferably, therefore, the agitating member should be disenabled throughout the inteval between the removal of the used cartridge and the insertion of a new cartridge. Suspending the agitating operation for such an interval is not critical because it will be resumed as soon as a new cartridge is loaded. Even during the above-mentioned interval, the copier should preferably be operated without interruption.
In the case of a two-component developer, toner is sequentially supplied to the developer as the toner concentration in the developer is decreased. The supply of toner is essential even in the case of a one-component toner. In an image forming apparatus of the type using a toner cartridge for the supply of toner and replacing the cartridge through an opening which is formed through a housing portion of the apparatus, toner adhered to the bottom wall of the used cartridge is apt to be scattered around or dropped through the opening due to vibrations when the cartridge is removed from the apparatus. Such toner would contaminate the exterior of the apparatus.